The use of mesh based global digital image correlation is proposed for measuring displacement fields around a crack tip and evaluating the fracture mechanics parameter, J-integral. The displacement gradients and the strains on the integration domain are determined from the measured displacement fields using a finite element smoothing technique. Then, the stresses are determined using the elastic-plastic constitutive relations with the strain incremental theory. J-integral values are then obtained by performing the numerical integration on the domain. The effectiveness is demonstrated by measuring the displacement fields around a crack of an aluminum specimen and evaluating J-integral. Results show that the near-tip displacement distributions are obtained accurately using mesh based digital image correlation with singular elements at the crack tip. Furthermore, the J-integral values can be obtained from the measured displacements by the proposed procedure.

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A longitudinal compressive modulus of carbon fiber was measured using a single fiber model composite. A single fiber was straightly embedded in an epoxy matrix, and its compression test was performed by means of four point bending test. Young's modulus of the epoxy matrix was reduced intentionally by changing the mixture ratio of epoxy resin/hardener to develop fiber micro-buckling. Two polyacrylonitrile carbon fibers with different longitudinal tensile modulus were provided for the experiment. An E-glass fiber with almost same diameter as the carbon fibers was used as a reference material. The micro-buckling wavelengths of the carbon fibers embedded in the epoxy resin were measured during the compression tests, from which the longitudinal compressive moduli were calculated. Estimated compressive moduli of the carbon fibers were found to be almost the same to each longitudinal tensile modulus.

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We aim to realize novel collagen/apatite composite materials, which have the optimally composed and layered microstructure, as artificial bone cartridges to bone defects by mimicking the real bone microstructures, in future. As the first step, we tried to evaluate the effect of synthesis condition on mechanical properties of collagen fibers as the unit structure of collagen/apatite artificial bone cartridges, based on the micro-tensile test. In addition, we tried to investigate the optimum synthesis condition, where realize the maximum tensile strength of collagen fibers. Here, we developed a micro-tensile testing device utilizing the deflection of cantilever beam. Single-fiber-like collagen fibers were prepared by bio-mimetic method, where fibrosis and cross-linking of collagen molecules are derived simultaneously. As the cross-linking agent, 1-ethyl-3-carbodiimide hydrochloride(EDC)was selected. As results, collagen fibers prepared under the EDC concentration of 10mmol/L was twice higher than those prepared without addition of EDC. In the range of higher EDC concentration than 20mmol/L, the tensile strength of collagen fibers decreased with increasing EDC concentration. EDC concentration of 60mmol/L did not derive fibrosis. Therefore, it is suggested that the EDC concentration, where fibrosis and cross-linking induce a synergistic effect, could optimize the microstructure of collagen fibers.

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This study is concerned with the molding conditions for stamping system of plain woven carbon fiber reinforced polycarbonate (CF/PC) laminates. Stamping system is consisted with two steps of processes. The first step is the process in which CF/PC laminated plates are molded using plain woven carbon fiber layers and PC films, and the second step is the process in which the laminated plates are formed by stamping. In the first step, the study of molding conditions is performed in the view point of appearance and mechanical properties. In the second step, the study of stamping conditions is performed in the view point of dimensional stability.

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